Gear stabilizer



Patented July 8, 1941 GEAR STABILIZER Percy C. Day, Brookfield, Wis., assignor to The Falk Corporation, Milwaukee, Wis., a corporation of Wisconsin Application January 28, 1938, Serial No. 187,359

(Cl. 74-410) s.

4 Claims.

This invention relates to gear stabilizers for use primarily in marine gear units of the multiple reduction "nested type.

Gear units of this type ordinarily include, in a single support or housing, a low speed shaft carrying the main or low speed gear, and an intermediate shaft carrying a pinion which meshes with and drives the main gear and also carrying a large gear by which it and the pinion are driven from a third shaft in the housing.

The main gear and pinion are ordinarily of the double-helical or herringbone type, so as to realize the recognized advantages of helical gear action and at the same time avoid the unbalanced axial thrust characteristic of single-helical gears. The gear on the intermediate shaft is also of the double-helical type, although it is commonly divided into separate single-helical gears of opposite hand disposed adjacent opposite ends of the pinion. The low speed shaft is usually confined against axial movement, while the intermediate shaft is ordinarily free to fioat axially in order to permit the herringbone pinion to properly ad- J'ust itself to the main gear and thereby obtain a smooth gear action and automatic equalization of load upon the two helices of the pinion and of the main gear.

When applied to marine use, however, this free fioating condition of the heavy intermediate assembly, including the intermediate shaft with its pinion and gear, presents a serious problem. For instance, under the influence of ship movements, particularly when rolling and tossing in a rough sea, this heavy free floating assembly tends to shift back and forth, restrained only by engagement of the pinion with the main gear, and imposing, shocks and strains on the intermeshing teeth of the pinion and gear with consequent detrimental wear and tear on the gearing and the development of objectionable noise. This objectionable' condition is further aggravated by sudden fluctuations in load on the gearing commonly produced by momentary exposure of the driven propeller above water.

One object of the present invention is to overcome the above difiiculties by the provision of means for resisting Sudden axial movements of the intermediate assembly without interfering with the desirable automatic self-adjusting action of the pinion with respect to the main gear.

Furthermore, in marine gearing the shafts are commonly somewhat inclined to correspond to the inclination of the propeller shaft, so that the free fioating intermediate assembly tends to shift axially in the 'direction of inclination and to impose an undue burden on one helix of the double helical pinion and main gear.

Another object of this invention is 'to compensate at least in part, for this unbal'anced condition.

Other more specific objects and advantages will appear from the following description ofv an llustrative embodiment of the presentinvention.

In the accompanying drawing- Figure 1 is a Vertical sectional view of a floating intermediate assembly of a "nested gear set equipped With a stabilizer constructed in accordance with the present invention.

Fig. 2 is a sectional detail View on a larger scale.

The intermediate assembly shown constitutes a part of a conventional multiple reduction gear unit of the "nested type and includes a large hollow shaft Ii! journalled at opposite ends in appropriate bearings ll in opposite side Walls |2 of a standard housing. The shaft IO carries the usual ntergal double helical pinion M which meshes with and drives the usual double helical main gear |5, axially fixed within the housing. The shaft IO also carries the usual pair of single helical gears IB of opposite hand through which the shaft Ill is driven.

It will be noted that the bearings Il are such as to permit free axial movement of the shaft IO so as to permit the pinion I 4 to automatically adjust itself to the main gear 15 in the usual manner. In this instance, however, a stabilizer has been provided, designed to resist sudden aXial movements of the shaft l for the purpose hereinabove'noted, without interfering with the normal self-centering function of the pinion.

Although the stabilizer may assume various forms, that shown includes a piston vl'i rigidly secured to a supporting stub shaft I8 carried by and'projecting coaxially from theshaft |0. In this instance the shaft |8 constitutes an integral part of a supporting disk |9 securely anchored to the end of the shaft Ill by bolts or otherwise.

The periphery 28 of the piston ll is minutely spaced from the periphery of a surrounding concentric stationary drum 2| which is completely filled with oil, or other suitable liquid, preferably under pressure. In order to accurately maintain a concentric relation between the drum and piston, an-d thereby preserve a substantially uniform clearance between the peripheries thereof, the drum is also preferably supported by the stub shaft IB. For that purpose the end heads 22 of the drum are provided With suitable bearings 23, each having a close rotating fit with the shaft IS. With this arrangement it will be noted that the drum and piston will follow, as a unit, any radial displacement of the shaft |8 resulting from radial displacement of the shaft IO in its bearings l or from any other cause.

The drum 2 I, however, is confined against axial displacement by and between opposed thrust-sustaining rings 24 formed within a stationary auXiliary housing V25 bolted or otherwise fixed to the main housing |2 and enclosing the drum 2|. The annular faces of the rings 24 are machined and bear closely against machined annular pads 26 on the end heads 22 of the drum. The drum is also restrained against rotation by ap-propriate means such as a hardened steel pin or key 21 carried by the housing 25 and loosely engaged. Within a socket 'I' formed in the drum.

The drum 2| is marntained fiooded with oil or other liquid from an appropriate pressure source through a pipe 28 and flexible conduit 29. Suitable vent holes 3G in the top of the drum provide for the escape of air from the drum during fillin'g, and are vordinarily closed by appropriate means, such as plugs or cocks, after the drum has been filled.

From the foregoing it will be noted that the piston l'l, fixed to the shaft IO, reacts against the liquid in one end or the other of the stationary drum 2| to resist any Sudden axial movement of the shaft IO, yet the slight by-passing of liquid from one end of the drum to the other, through the minute running clearance between the peripheries of piston and drum, permits a gradual axial movement of piston and shaft I such as may be required to permit the pinion 14 to adjust itself to the main gear in the usual manner. In order to better sustain Sudden axial thrusts the periphery of the piston is preferably provided with labyrinth grooves 3| to more effectively reduce the by-passing of liquid through the clearance between the piston and drum. Likevvise the bearings 23 for the drum are alsoprovided With labyrinth grooves 32 to better resist leakage of liquid from the drum.

The stabilizer shown is designed also to maintain an axial thrust upon the shaft I!! in a manner to compensate Wholly or in part, for the thrust which normally results from an inclined mounting of the shaft Within the ship, it being understood, of course, that in marine gearing the shafts `are commonly inclined to correspond to the inclination of the propeller shaft. In this instance the stabilizer is designed for mounting on the lower or down-hill end of the shaft IO and to impose a thrust toward the left (Fig. 2) contrary to the thrust normally resulting from the downward inclination of the shaft toward the stabilizer. For this purpose the outer end l8' of the stub shaft |8 is reduced, so that the effective pressure area on that end of the piston l'l is somewhat greater than the pressure area on the inner end thereof, and so that the pressure of the oil in the drum 2! consequently imposes a thrust upon the piston toward the left, the magnitude of the thrust depending upon the difference between the pressure areas and also upon the degree of oil pressure maintained in the supply pipe 28.

Various changes may be made in the embodiment of the invention hereinabove specifically described Without departing from or sacrificing the advantages of the invention as defined in the appended claims.

I claim:

1. In a gear set the combination of an axially moveable gear-carrying shaft, a liquid filled cylinder member, a piston member coacting with the liquid in said cylinder member for yieldably resisting relative axial movement therebetween, and means engaged With said shaft and with both of said members for maintaining said members Jcoaxial with said shaft in all variations in position of the axis of said shaft, one of said members being axially fixed and the other of said members reacting on said shaft to cushion the latter against Sudden axial displacement.

2. In a gear set the combination of an axially moveable ro-tary gear-carrying shaft, a liquidfilled cylinder mounted upon said shaft and disposed coaxially therewith, means confining said cylinder against rotation and against axial movement, and a piston connected for rotation with said shaft and coacting With the liquid in said cylinder to cushion said shaft against sudden axial movement.

3. In a gear set the combination of an axially moveable rotary gear-carrying shaft, a piston connected for movement as a unit With said shaft, a non-rotary axially fixed liquid-filled cylinder surrounding said piston and coacting therewith to cushion said shaft against sudden axial movement, said piston and cylinder being supported by said shaft and centered solely thereby and being also arranged to provide a 'slight Working clearance between the peripheries thereof, and means for maintaining an accurate concentric relation between said piston and cylinder to thereby accurately maintain said Working clearance.

4. In a marine gear set the combination of an aXially moveable gear-carrying shaft, an axially fixed liquid-filled chamber, a piston fitted Within said Chamber with a predetermined clearance therebetween, said piston and said Chamber being both supported by said 'shaft and being l`accurately positioned thereby With respect to each other, said piston coacting vvith the liquid in said chamber and With said shaft to cushion the latter against sudden axial displacement.

PERCY C. DAY. 

